AudioKit Conflict between Midi Instrument and Mic behavior - swift

Question

I am trying to make my app produce midi notes at the same time listening to the input from the mic:
var engine = AudioEngine()
var initialDevice: Device!
var mic: AudioEngine.InputNode!
var tappableNodeA: Fader!
var tappableNodeB: Fader!
var tappableNodeC: Fader!
var silence: Fader!
var tracker: PitchTap!
private var instrument = MIDISampler(name: "Instrument 1")
func noteOn(note: MIDINoteNumber) {
instrument.play(noteNumber: note, velocity: 90, channel: 0)
}
func noteOff(note: MIDINoteNumber) {
instrument.stop(noteNumber: note, channel: 0)
}
override func viewDidLoad() {
super.viewDidLoad()
print("init started ")
guard let input = engine.input else { fatalError() }
guard let device = engine.inputDevice else { fatalError() }
print("input selected")
initialDevice = device
engine.output = instrument
mic = input
tappableNodeA = Fader(mic)
tappableNodeB = Fader(tappableNodeA)
tappableNodeC = Fader(tappableNodeB)
silence = Fader(tappableNodeC, gain: 0)
engine.output = silence
print("objects init")
tracker = PitchTap(mic) { pitch, amp in
DispatchQueue.main.async {
self.update(pitch[0], amp[0])
}
}
start()
// other init that are not related
}
The start function is written below:
func start() {
do {
if let fileURL = Bundle.main.url(forResource: "Sounds/Sampler Instruments/sawPiano1", withExtension: "exs") {
try instrument.loadInstrument(url: fileURL)
} else {
Log("Could not find file")
}
} catch {
Log("Could not load instrument")
}
do {
try engine.start()
tracker.start()
} catch let err {
print("caught error at start")
Log(err)
}
}
As long as I making the first try call to set up the instrument I get the following error:
*** Terminating app due to uncaught exception 'com.apple.coreaudio.avfaudio', reason: 'required condition is false: _engine != nil
Why the would the condition be false?

Answer 1

Ok, so the solution was to separate the calls into two functions, and position the first call before tapNode configuration:
var engine = AudioEngine()
var initialDevice: Device!
var mic: AudioEngine.InputNode!
var tappableNodeA: Fader!
var tappableNodeB: Fader!
var tappableNodeC: Fader!
var silence: Fader!
var tracker: PitchTap!
private var instrument = MIDISampler(name: "Instrument 1")
func noteOn(note: MIDINoteNumber) {
instrument.play(noteNumber: note, velocity: 90, channel: 0)
}
func noteOff(note: MIDINoteNumber) {
instrument.stop(noteNumber: note, channel: 0)
}
override func viewDidLoad() {
super.viewDidLoad()
print("init started ")
guard let input = engine.input else { fatalError() }
guard let device = engine.inputDevice else { fatalError() }
print("input selected")
initialDevice = device
engine.output = instrument
start1()
mic = input
tappableNodeA = Fader(mic)
tappableNodeB = Fader(tappableNodeA)
tappableNodeC = Fader(tappableNodeB)
silence = Fader(tappableNodeC, gain: 0)
engine.output = silence
print("objects init")
tracker = PitchTap(mic) { pitch, amp in
DispatchQueue.main.async {
self.update(pitch[0], amp[0])
}
}
start()
// other init that are not related
}
func start1(){
do {
if let fileURL = Bundle.main.url(forResource: "Sounds/Sampler Instruments/sawPiano1", withExtension: "exs") {
try instrument.loadInstrument(url: fileURL)
} else {
Log("Could not find file")
}
} catch let err {
Log("Could not load instrument")
Log(err)
}
}
func start() {
do {
try engine.start()
tracker.start()
} catch let err {
print("caught error at start")
Log(err)
}
}
Although the exception is now gone, there is still no sound being played for some reason.